1. Field of the Invention:
This invention relates to a pump adapted to generate lift in a working fluid by rotating an impeller in a fluid passage.
2. Description of the Prior Art:
A regenerative pump consists of a casing having therein an annular fluid passage communicated with a suction port and a discharge port of the casing, an impeller provided on the outer circumferential surface thereof with a vane fitted and adapted to be rotated in the fluid passage in the casing, a rotary shaft supported rotatably by the casing and having the impeller mounted unitarily thereon, and a mechanical seal fitted on the outer circumferential surface of the rotary shaft so as to prevent a working fluid, which flows in the fluid passage and contacts the outer circumferential surface of the rotary shaft, from leaking to the outside of the casing.
The vane of the impeller consists of a plurality of radially extending blades, and recesses provided among these blades.
When the rotary shaft is driven by a motor to rotate the impeller, the working fluid in the recesses in the vane of the impeller flows out from the outer circumferential portion of the vane into the fluid passage, and the working fluid in the fluid passage flows from a side portion of the vane into the recesses therein. The working fluid receives a pressure energy and velocity energy due to the centrifugal force generated by the rotating impeller, and the velocity energy is converted into pressure energy in the fluid passage. These operations are carried out repeatedly in the recesses in the vane of the impeller. Accordingly, the fluid pressure increases, and the working fluid is discharged from the discharge port.
The regenerative pump described above is constructed so that the impeller is rotated in a non-casing-contacting state, and the working fluid flows to the rotary shaft, on which the impeller is mounted, through the clearance between the impeller and the inner surface of the casing. Therefore, the leakage of the working fluid is prevented by the mechanical seal provided on the rotary shaft. This mechanical seal has a mechanical slide surface contacting the working fluid, and is necessarily subject to wear. The abrasion powder occurring as this mechanical slide surface is worn is mixed in the working fluid, and the abrasion powder-mixed working fluid is discharged through the fluid passage. Consequently, when the working fluid consisting, for example, of pure water which requires that no impurities mixed therein, such a conventional regenerative pump cannot be used.
In the conventional regenerative pump, further the vane of the impeller is formed so that the axis of a blade and the bottom portion of a recess in the vane extend at substantially right angles to cause an angular portion to occur between the blade and recess. Accordingly, the working fluid advancing from a side portion of the vane toward the outer circumferential portion thereof through the recesses does not flow smoothly at such angular portions. For example, when the working fluid consists of water, the microorganisms and impurities contained therein are deposited and accumulated on these angular portions. The same applies to a pump provided in its casing with a fluid passage having angular portions, i.e. a substantially square cross section.